1. The Field of the Invention
This invention relates generally to fluid flow measurements. More specifically, the invention relates to a system for measuring wind movement in three dimensions, thereby enabling a user to not only measure wind velocity and direction, but other meteorological information which can be derived therefrom, including the measurement of severe wind conditions such as wind shear.
2. The State of the Art
The state of the art in three dimensional fluid flow measurements is replete with examples of devices which attempt to determine the direction and velocity of wind. However, there are many different approaches which have been attempted. Furthermore, these different approaches have been met with varying degrees of success. In addition, some of these approaches are not suitable for severe weather conditions.
A brief examination of some of the prior art is provided in order to illustrate some of the shortcomings thereof. Beginning with U.S. Pat. No. 3,359,794 issued to Rosenberg, the patent apparently teaches a plurality of thermistors which are coupled to the outside of a sphere. The thermistors measure an increasing temperature of the fluid (in this case water) as it flows around the current meter. This information is used to determine a flow direction and velocity. It is observed that the fluid must be of a type which will measurably rise in temperature as it flows around the sphere. Among other things, a substantial number of thermistors must be used. The patent also states that it is specifically intended for determining current data for a liquid.
In U.S. Pat. No. 3,695,103 issued to Olson, the patent teaches a buoyant sphere which is floating in a medium (liquid). The sphere is tethered to cables which have strain gauges. This application is also directed to liquid applications.
In U.S. Pat. No. 4,488,431 issued to Miga, the patent teaches a wind speed and direction device which is very similar to anemometers such as the one shown in FIG. 1.
FIG. 1 is provided to illustrate the problems with a state of the art anemometers 2 and wind vanes 4. For example, because it is mechanical, light wind conditions might not overcome the frictional component of the wind vane. The result is an increasingly incorrect and sluggish response of the vane 4. As is typical of mechanical sensors, they become non-responsive or slow to respond at low wind speeds. The anemometer 2 suffers from being inaccurate in light wind conditions, and being slow to respond to quickly changing conditions. Furthermore, both devices can easily fail in severe weather conditions such as icing or snow.
In U.S. Pat. No. 4,920,808 issued to Sommer, the patent teaches a device for measuring wind direction and velocity. However, the method and apparatus are unnecessarily complicated by the use of a body other than a sphere. Among other things, the patent also teaches having different systems for determining flow direction and velocity. For example, the device requires a servo-motor and other high maintenance parts for determining direction of flow, and other sensors for calculating the velocity.
There are other teachings in U.S. Pat. No. 4,631,958 issued to Van Cauwenberghe et al, in U.S. Pat. No. 4,635,474 issued to Blackwood, and in U.S. Pat. No. 5,117,687 issued to Gerardi, all of which operate using different principles of operation, and which are designed to determine wind velocity and direction.
What is needed is a system for isotropically measuring the direction and velocity of wind which is substantially less complicated than the prior art. It would be another advantage if the system could also be modified to withstand the elements so that measurements can be made in hostile environments. What is also needed is a system which can be linked together from a plurality of measurement stations to thereby use data which is accumulated about a larger area to thereby make predictions and/or actual measurements of dangerous wind conditions such as wind shear by extrapolating data therefrom.